Papers by Keyword: Parametric Uncertainty

Abstract: In this paper, an unmanned aerial vehicle (UAV) with fixed-wing in normal condition flight, and fixed height, is considered and along with this process, kinematics model of UAV, assumed to have parametric uncertainty. In this situation the target of designing of proper controller family, based on switching logic, is to control the speed and roll angle of fixed-wing unmanned aerial vehicle in order to track desired path with minimum error. The desired path will be generated by trajectory maker block. The results of simulation on a fixed-wing UAV are presented to show the efficiency of the method.

Abstract: This paper proposes the design of a robust nonlinear optimal controller to move the underwater vehicle in the depth channel using gradient descent method. A nonlinear model with six degrees of freedom (6-DOF) has been extracted for the underwater vehicle. To selection of the model and design of controller, conventional assumptions used for other controllers have not been considered and the developed controller can be implemented via at least assumptions. In presented control method, systematic step selection for solving of the algorithm has increased the rate of convergence significantly. The performances of the proposed robust controller for moving in depth channel with considering of parametric uncertainty for the model have been confirmed via some simulations. The results show the desirable performance of developed controller.

Abstract: A nonlinear model of 4WS vehicle with three degree-of-freedom is established, Considering the uncertain characteristic of the tire lateral stiffness, an guaranteed cost control scheme was proposed for vehicle stability control, the optimal guaranteed cost control laws is derived in terms of linear matrix inequalities (LMIs). The simulation results show that transient response amplitude of the yaw rate , center side-slip angle and lateral acceleration can be decreased greatly, a good steady-state response can be achieved at a high speed, which improves the driving safety and handling stability.

Abstract: The robust stabilization design problem for the continuous time-delay systems subjected to parametric uncertainties is addressed in this paper. The uncertainties are time-varying. By using the Riccati equation approach associated with some linear algebraic techniques and an upper bound of the solution of the Riccati equation, a new stabilizability criterion and the corresponding control design are proposed. This criterion is independent of the Riccati equation and hence is easy to be tested and the corresponding controller is also easy to be implemented. It is shown that the criterion is sharper than a previous one. A numerical algorithm is also proposed to construct the controller.

Abstract: In this paper, we develop a new robust adaptive control scheme for ship steering by introducing alternative smooth function and Nussbaum function into backstepping approaches. And no requirements for the knowledge of control coefficient and the bound of unknown external disturbance, the proposed strategy implements the global stability of the ship course control and guarantees the global uniform boundedness of all signals of the resulting closed-loop system. Theoretical analysis demonstrates that tracking error asymptotically converges within an arbitrary small value pre-described by designer. Simulation results illustrate the effectiveness of the developed adaptive backstepping control law.

Abstract: The discrete-time adaptive sliding mode controller for spinning rockets in presence of parameter error is proposed. Considering the nonlinear characteristics for the system, input-output feedback linearization is utilized to transform the system model into two standard form subsystems. Then a discrete-time controller for guided rockets is designed based on discrete-time sliding mode control principle. In order to diminish the switch width of the discrete-time sliding mode system corresponding to parameter error, a dead-zone parameter adaptive law is designed. The stability of the uncertain closed-loop system is proved by Lyapunov theory, which make the controller have high robustness. Simulation result indicates that the proposed controller is robust with respect to large aerodynamic parametric uncertainty, and has excellent dynamic tracking performance.

Abstract: The aircraft tire friction force varies significantly with different types of runway materials, surface lubricity and vertical load, which affects the braking efficiency. In this paper, the dynamic LuGre model is introduced to describe the friction force, which could give a projective mapping from the physical unknown runway state to mathematical friction force model with parametric uncertainties. The state observers are employed to estimate the unmeasurable internal friction states of the friction force model and the estimates are substituted into the parameter adaptive law to obtain the current runway state. The pseudo-static friction force model is calculated online to obtain the maximum friction coefficient and its slip ratio. This slip ratio is set as the tracking target for the well-designed feed-forward controller based on the feedback linearization method. The simulation results are shown to verify the proposed method.

Abstract: The problem of adaptive control design of ship autopilot with rudder dynamics is studied. The model is described by a third order nonlinear model for parametric uncertainties. An adaptive neural network (NN ) control algorithm based on dynamic surface control (DSC) is developed. With only one learning parameter and reduced computation load, the proposed algorithm can avoid both problem of explosion of complexity in the conventional backstepping method and singularity problem. In addition, the boundedness stability of the closed-loop system is guaranteed and tracking error can be made arbitrary small. The effectiveness of the presented autopilot has been demonstrated in the simulation.

Abstract: In the real automated highway system, various factors to vehicles which are moving make the velocity of vehicles change suddenly. In this paper, assuming that the mass of vehicles, the drag coefficient and the resistance of the ground were uncertain, the controller for a class of time-varying delayed look-ahead vehicle longitudinal following system with impulsive effect was designed by using the idea of quasi-sliding mode control. An example is given at last to test the controller proposed in this paper.

Abstract: The main theme of this paper is to present robust guaranteed cost control laws for a class of fuzzy bilinear systems (FBS) with parametric uncertainties. First, the piecewise Lyapunov function (PLF) method is utilized to design a fuzzy controller, which ensures the robust asymptotic stability of the closed-loop system, and then the robust guaranteed cost control law is also proposed. Second, based on the Schur complement and some variable transformations, some sufficient conditions are derived to guarantee the stability of the overall fuzzy control system via linear matrix inequalities (LMIs). Finally, a numerical example is utilized to demonstrate the validity and effectiveness of the proposed control scheme.